1. Field of the Invention
The present invention relates to compressor pistons for use in compressors or pumps, and more particularly, to pistons for use in fluid displacement apparatus, such as swash plate-type compressors.
2. Description of Related Art
Pistons having hollow structures at their head portions, which slide in cylinder bores of a compressor and maintain airtightness or watertightness between an exterior surface of the head portion and an interior wall of the cylinder bore, are known in the art. For example, Japanese Patent Unexamined Publication No. 11-303747 describes a piston having a hollow structure at its head portion, which is shown in FIGS. 4a-4h. 
Referring to FIGS. 4a-4h, a piston 13xe2x80x3 has a hollow head portion, which comprises an end portion 131xe2x80x3 and a cylindrical portion 132xe2x80x3. Therefore, piston 13xe2x80x3 has an advantage that it is lightweight. Moreover, to realize a further reduction in piston weight, a pair of penetrating apertures 136xe2x80x3 are pierced through cylindrical portion 132xe2x80x3 at its end on the side of connecting portion 134xe2x80x3. However, piston 13xe2x80x3 has a disadvantage that the strength of a circumference portion(s) of penetrated aperture(s) 136xe2x80x3 may decrease. As a result, when the compressor is operated under high load, a crack C, e.g., as shown in FIG. 4f, may originate from the circumference portion(s) of penetrated aperture(s) 136xe2x80x3.
A need has arisen to reduce or eliminate the above-mentioned problems, which may be encountered in known compressor pistons with hollow head portions having penetrating apertures that realize piston weight reductions.
In an embodiment of this invention, a piston for use in a fluid displacement apparatus, such as a swash plate-type compressor, comprises a head portion and a connecting portion. The head portion has a cylindrical shape and a hollow structure. The connecting portion extends from an end surface of the head portion and couples the piston with a moving source. An aperture is formed through the end surface of the head portion adjacent to the connecting portion. A rib is formed adjacent to the aperture.
In another embodiment of this invention, a piston for use in a fluid displacement apparatus, such as a swash plate-type compressor, comprises a head portion and a connecting portion. The head portion has a cylindrical shape and a hollow structure. The head portion comprises an end portion and a cylindrical portion. The end portion is fixedly connected to the cylindrical portion. The connecting portion extends from an end surface of the cylindrical portion and couples the piston with a moving source. A pair of apertures are formed through the end surface of the cylindrical portion adjacent to the connecting portion. A rib is formed between the pair of apertures.
Objects, features, and advantages of embodiments of this invention will be apparent to persons of ordinary skill in the art from the following detailed description of the invention and the accompanying drawings.